Imagine you are working on a project based based upon a traditional 3 layers architecture, where the layers are named presentation, business logic, integration. Of course, you want each layer to be independant of all the other layers and so you want to produce one artifact for each one. Following the Maven norm, you will need to have one project for each layer. Hence, your setup should look like this :
So to compile your presentation project, you will first need to compile the business logic project. But wait, the business logic project upon the integration project so it should be compiled first. Ok, let us recapitulate, so to compile your presentation project you will need to type the followings command (we assume the projects have been put in a common root directory):
8 lines just to compile! I thought Maven was simple. Of course, Maven offers a solution to this problem in the form of multi-modules project.
A multi-modules project is a very particular type of project - it doesn't produce any artifact and is composed of several other projects. When you run a command on the project, it will executes it on all its children projects. Even better, Maven is able, throught its reactor component (don't worry about it for now), to discover the correct execution order and to detect circular dependencies. So let's apply this solution to the last example :